Polymer synthesis

ABSTRACT

Disclosed is a method of preparing emulsion polymers and a method of preparing porous dielectric materials using the emulsion polymers.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to the field of polymersynthesis. In particular, the present invention relates to the field ofemulsion polymer synthesis.

[0002] Polymers have been prepared by a variety of means such assolution polymerization and emulsion polymerization. Emulsionpolymerization is advantageous in that polymer particles having smallparticle sizes and particle size polydispersities approaching 1 can beprepared. Typically, such emulsion polymerizations are performed usingionic surfactants.

[0003] For many polymer applications, such as paints, ionic surfactantsused during emulsion polymerization pose no problems. However, for otherapplications, such as those in the electronics industry, such ionicsurfactants are problematic.

[0004] One application of polymers in the electronics industry is in theformation of porous interlayer dielectric materials used in themanufacture of integrated circuits. As electronic devices becomesmaller, there is a continuing desire in the electronics industry toincrease the circuit density in electronic components, e.g., integratedcircuits, circuit boards, multichip modules, chip test devices, and thelike without degrading electrical performance, e.g., crosstalk orcapacitive coupling, and also to increase the speed of signalpropagation in these components. One method of accomplishing these goalsis to reduce the dielectric constant of the interlayer, or intermetal,insulating material used in the components. A method for reducing thedielectric constant of such interlayer, or intermetal, insulatingmaterial is to incorporate within the insulating film very small,uniformly dispersed pores or voids. Preferred are pores or voids havinga diameter of less than or equal to 100 nm.

[0005] One known process of making a porous dielectric involvesdispersing thermally removable solid particles, i.e. porogens, in aB-staged dielectric precursor, polymerizing the dielectric precursorwithout substantially removing the particles, followed by heating thedielectric material to substantially remove the particles and therebyleaving voids or free spaces in the dielectric material. Such voidsreduce the dielectric constant of the dielectric material. See, forexample, U.S. Pat. No. 5,895,263 (Carter et al.).

[0006] Emulsion particles are particularly suited for preparing porousdielectric materials due to their controlled particle size range andnarrow particle size distribution. See, for example, Antonietti et al.,Synthesis and Size Control of Polystyrene Latices via Polymerization inMicroemulsion, Macromolecules, vol. 24, 1991, pp 6636-6643. One problemwith such decomposable polymer approach is that some of the polymericmaterial may remain in the pores after the polymers have been removed.This is particularly true of ionic material which is typically lessvolatile and more likely to remain in the pores. As the dielectriclayers become smaller, the presence of even small amounts of ionicmaterial can lead to cross-talk or shorts. Thus, conventional emulsionpolymers, prepared with an ionic surfactant, are not suitable for use inthe manufacture of porous dielectric materials.

[0007] While other methods of preparing porous dielectric materials areknown, they suffer from broad distributions of pore sizes, too largepore size, such as greater than 20 microns, or technologies that are tooexpensive for commercial use, such as liquid extractions undersupercritical conditions.

[0008] It is known that ionic surfactants can be removed from smallemulsion polymer particles by treatment with ion-exchange resins or bysuccessive washing of the isolated particles as described by Krieger.However, these approaches are cumbersome and time consuming.

[0009] Emulsion polymerizations using only ethoxylated alcoholsurfactants, a nonionic surfactant, are known. Such emulsionpolymerizations are typically inefficient, requiring high soap levelsand low solids content. The particles produced by such polymerizationshave a particle size in the range of several hundreds of nanometers.U.S. Pat. No. 5,502,105 (Revis) discloses a method of making a siliconeemulsion by dispersing a siloxane in water by forming a mixture ofwater, a cyclic siloxane and an ethoxylated alcohol nonionic surfactant;adding an organosilanolate polymerization initiator, and heating themixture to polymerize the cyclic siloxane. This patent does notdisclosed cross-linked emulsion particles.

[0010] There is thus a need for a method of producing cross-linkedemulsion polymer particles that are substantially free of ionicsurfactants, particularly for use in electronics applications, and donot require extensive post polymerization treatments.

SUMMARY OF THE INVENTION

[0011] It has been surprisingly found that emulsion polymers havingsmall particle sizes can be prepared in a non-ionic surfactant.Non-ionic surfactants are surprisingly capable of producing extremelysmall polymer particles less than 100 nm in size. Such polymers have amuch lower level of ionic contaminants than conventionally producedemulsion polymers.

[0012] In one aspect, the present invention provides a process forpreparing polymer particles including the step of: polymerizing one ormore monomers in an aqueous emulsion including one or more surfactants,the one or more surfactants consisting of nonionic surfactants, whereinat least one of the nonionic surfactants is an amine-N-oxide surfactant,and wherein the polymer particles have a mean particle size of less thanor equal to 100 nm.

[0013] In a second aspect, the present invention provides an emulsion ofpolymer particles including one or more surfactants, the one or moresurfactants consisting of nonionic surfactants, wherein at least one ofthe nonionic surfactants is an amine-N-oxide surfactant, and wherein thepolymer particles have a mean particle size of less than or equal to 100nm.

[0014] In a third aspect, the present invention provides an emulsion ofpolymer particles including one or more surfactants, wherein the polymerparticles have a mean particle size of less than or equal to 100 nm, andwherein the emulsion is substantially free of ionic surfactants.

[0015] In a fourth aspect, the present invention provides a compositionincluding a B-staged dielectric material and an emulsion polymericporogen particle wherein the polymer particles have a mean particle sizeof less than or equal to 100 nm, and wherein the polymer particles aresubstantially free of ionic surfactants.

[0016] In a fifth aspect, the present invention provides a method ofmanufacturing an electronic device including the steps of: a) depositingon a substrate a layer of a composition including B-staged dielectricmaterial having a plurality of emulsion polymeric porogen particlesdispersed therein, wherein the porogen particles have a mean particlesize of less than or equal to 100 nm, and wherein the porogen particlesare substantially free of ionic surfactants; b) curing the B-stageddielectric material to form a dielectric matrix material withoutsubstantially removing the porogen particles; c) subjecting thedielectric matrix material to conditions which at least partially removethe porogen particles to form a porous dielectric material layer withoutsubstantially degrading the dielectric material; d) patterning thedielectric layer; e) depositing a metallic film onto the patterneddielectric layer; and f) planarizing the film to form an electronicdevice.

DETAILED DESCRIPTION OF THE INVENTION

[0017] As used throughout this specification, the followingabbreviations shall have the following meanings, unless the contextclearly indicates otherwise: ° C.=degrees centigrade; nm=nanometer;g=gram; wt %=weight percent; L=liter; mL=milliliter; w/w=weight perweight basis; SLS=sodium lauryl sulfate; ALS=ammonium lauryl sulfate;A-MSTY=alpha-methylstyrene; and MMA=methyl methacrylate.

[0018] The term “(meth)acrylic” includes both acrylic and methacrylicand the term “(meth)acrylate” includes both acrylate and methacrylate.Likewise, the term “(meth)acrylamide” refers to both acrylamide andmethacrylamide. “Alkyl” includes straight chain, branched and cyclicalkyl groups. The term “porogen” refers to a pore forming material, thatis a polymeric material or particle dispersed in a dielectric materialthat is subsequently removed to yield pores, voids or free volume in thedielectric material. Thus, the terms “removable porogen,” “removablepolymer” and “removable particle” are used interchangeably throughoutthis specification. The terms “pore,” “void” and “free volume” are usedinterchangeably throughout this specification. “Cross-linker” and“cross-linking agent” are used interchangeably throughout thisspecification. “Polymer” refers to polymers and oligomers. The term“polymer” also includes homopolymers and copolymers. The terms“oligomer” and “oligomeric” refer to dimers, trimers, tetramers and thelike. “Monomer” refers to any ethylenically or acetylenicallyunsaturated compound capable of being polymerized. Such monomers maycontain one or more double or triple bonds.

[0019] The term “B-staged” refers to uncured dielectric matrixmaterials. By “uncured” is meant any dielectric material that can bepolymerized or cured, such as by condensation, to form higher molecularweight materials, such as coatings or films. Such B-staged material maybe monomeric, oligomeric or mixtures thereof. B-staged material isfurther intended to include mixtures of polymeric material withmonomers, oligomers or a mixture of monomers and oligomers.

[0020] Particle sizes were determined using standard dynamic lightscattering techniques. All correlation functions were converted tohydrodynamic sizes using LaPlace inversion methods, such as CONTIN. Allamounts are percent by weight and all ratios are by weight, unlessotherwise noted. All numerical ranges are inclusive and combinable inany order, except where it is obvious that such numerical ranges areconstrained to add up to 100%.

[0021] It has been surprisingly found that polymer particles having aparticle size of ≦100 nm can be prepared by emulsion polymerizationwithout the use of ionic surfactants. The emulsions of the presentinvention are formed using one or more nonionic surfactants, wherein atleast one of the nonionic surfactants is an amine-N-oxide surfactant.Thus, the present invention provides a process for preparing polymerparticles including the step of: polymerizing one or more monomers in anaqueous emulsion including one or more surfactants, the one or moresurfactants consisting of nonionic surfactants, wherein at least one ofthe nonionic surfactants is an amine-N-oxide surfactant, and wherein thepolymer particles have a mean particle size of less than or equal to 100nm.

[0022] The nonionic surfactants of the present invention include atleast one amine-N-oxide surfactant. The amine oxides are nonionicsurfactants obtained by oxidizing a tertiary amine to form the amineoxide. Amine oxide surfactants include the N-alkyl amine oxides such asN-cocadimethylamine oxide, N-lauryl dimethylamine oxide, N-myristyldimethylamine oxide, and N-stearyl dimethylamine oxide; the N-acyl amineoxides such as N-cocamidopropyl dimethylamine oxide andN-tallowamidopropyl dimethylamine oxide; and N-alkoxyalkyl amine oxidessuch as bis(2-hydroxyethyl) C₁₂-₁₅ alkoxypropylamine oxide. Thehydrophobic portion of the amine oxide surfactants is generally providedby a fatty hydrocarbon chain containing from ten to twenty-one carbonatoms.

[0023] Exemplary amine oxide surfactants include, but are not limitedto, lauric acid diethanolamide, N-lauryl dimethylamine oxide, coconutacid diethanolamide, myristic acid diethanolamide, and oleic aciddiethanolamide. Suitable commercial materials are those products soldunder tradenames and trademarks such as AMMONYX by the Stephan Company,Northfield, Ill.; BARLOX by Lonza Incorporated, Fairlawn, N.J.; andMACKAMINE by The McIntyre Group Limited, University Park, Ill. It willbe appreciated by those skilled in the art that one or more anime-oxidesurfactants may be used in the present invention. Typically, theanime-N-oxide surfactant is used in the present invention in an amountfrom 0.1 to 15% by weight, based on the total weight monomer andoptional cross-linker, preferably from 1 to 12 wt %, and more preferablyfrom 3 to 12 wt %.

[0024] A wide variety of nonionic surfactants may be used in combinationwith the amine-oxides. Suitable other nonionic surfactants include, butare not limited to, ethoxylated fatty alcohols, fatty acidalkanolamides, sorbitan derivatives, ethylene oxide/propylene oxidecopolymers, and the like. Such other surfactants may be used in a widevariety of amounts, such as from 0.1 to 15% by weight, based on thetotal weight of monomers and optional cross-linker, and preferably from2 to 12 wt %.

[0025] Fatty alcohol ethoxylates contain in their molecule thecharacteristic group—(OCH₂CH₂)_(a)OH, which is attached to a fattyhydrocarbon residue of about eight to twenty carbon atoms, such aslauryl (C₁₂), cetyl (C₁₆) and stearyl (C₁₈). The integer “a” can have avalue of one to about one hundred, but typically has a value of about 12to 40. Suitable fatty alcohol ethoxylates include, but are not limitedto, the various polyoxyethylene fatty alcohols sold under the tradenameBRiJ by ICI Americas Incorporated, of Wilmington, Del.; the tradenameEMERY by the Henkel Corporation/Emery Group, of Ambler, Pa.; thetrademark ETHOSPERSE by Lonza Incorporated, of Fairlawn, N.J.; and thetrademark PROMULGEN by the Amerchol Corporation, of Edison, N.J. Otherpolyoxyethylene fatty alcohols which can be employed in accordance withthe concepts of the present invention are polyoxyethylene (4) laurylether, polyoxyethylene (2) cetyl ether, polyoxyethylene (10) cetylether, polyoxyethylene (20) cetyl ether, polyoxyethylene (2) stearylether, polyoxyethylene (10) stearyl ether, polyoxyethylene (20) stearylether, polyoxyethylene (21) stearyl ether, polyoxyethylene (100) stearylether, polyoxyethylene (2) oleyl ether, polyoxyethylene (10) oleylether, and polyoxyethylene (20) oleyl ether. Other suitable nonionicsurfactants which are either ethoxylated alcohols or ethoxylated alkylphenols are sold under the trademarks TERGITOL and TRITON by UnionCarbide Corporation, Danbury, Conn.; NEODOL by Shell Chemical Company,Houston, Tex.; MACOL by PPG Industries, Gurnee, Ill.; and under thetradenames TRYCOL by Henkel Corporation, Ambler, Pa.; and BRIJ by ICIAmericas Incorporated, Wilmington, Del.

[0026] The fatty acid alkanolamides are nonionic surfactants obtained byreacting alkanolamines such as monoethanolamine, diethanolamine,monoisopropanolamine, or diisopropanolamine, with a fatty acid or fattyacid ester to form the amide. The hydrophobic portion of the nonionicsurfactant is provided by a fatty acid hydrocarbon chain which generallyhas from ten to twenty-one carbon atoms. The fatty acid alkanolamidesurfactants include fatty acid diethanolamides such as isostearic aciddiethanolamide, lauric acid diethanolamide, capric acid diethanolamide,coconut fatty acid diethanolamide, linoleic acid diethanolamides,myristic acid diethanolamide, oleic acid diethanolamide, and stearicacid diethanolamide; fatty acid monoethanolamides such as coconut fattyacid monoethanolamide; and fatty acid monoisopropanolamides such asoleic acid monoisopropanolamide and lauric acid monoisopropanolamide.Representative of a such nonionic surfactant is a product sold under thetrademark WITCAMIDE by Witco Corporation, New York, N.Y.

[0027] Suitable sorbitan derivatives are available under the tradenamesSPAN and TWEEN by ICI Americas Incorporated, Wilmington, Del.; andsuitable ethylene oxide/propylene oxide block copolymers are sold underthe trademarks PLURONIC and TETRONIC by BASF Corporation, Parsippany,N.J.

[0028] The nonionic surfactants of the present invention, particularlythe amine-oxide surfactants, are capable of producing extremely smallemulsion droplets. Controlled polymerization of the monomers in thesedroplets produces small polymer particles, i.e. ≦100 nm, and preferablyextremely small polymer particles, i.e. ≦50 nm in size. Emulsionpolymers having other suitable particle sizes, such as ≦45 nm, ≦40 nm,≦35 nm, and ≦30 nm, may be produced according to the present invention.Such polymer particles typically have a lower particle size of about 1nm. Thus, the present polymer particles have a particle size range offrom 1 to 100 nm, and preferably from 1 to 50 nm. The particle sizepolydispersity of these emulsion polymer particles is in the range1.0001 to 10, more preferably 1.001 to 5, and most preferably 1.001 to2.5.

[0029] A wide variety of monomers may suitably be used in the presentinvention. Suitable unsaturated monomers include, but are not limitedto: (meth)acrylic acid, (meth)acrylamides, alkyl (meth)acrylates,alkenyl (meth)acrylates, aromatic (meth)acrylates, vinyl aromaticmonomers, nitrogen-containing compounds and their thio-analogs, andsubstituted ethylene monomers. It will be appreciated by those skilledin the art that more than one monomer may suitable be employed.

[0030] Typically, the alkyl (meth)acrylates useful in the presentinvention are (C₁-C₂₄) alkyl (meth)acrylates. Suitable alkyl(meth)acrylates include, but are not limited to, “low cut” alkyl(meth)acrylates, “mid cut” alkyl (meth)acrylates and “high cut” alkyl(meth)acrylates.

[0031] “Low cut” alkyl (meth)acrylates are typically those where thealkyl group contains from 1 to 6 carbon atoms. Suitable low cut alkyl(meth)acrylates include, but are not limited to: methyl methacrylate(“MMA”), methyl acrylate, ethyl acrylate, propyl methacrylate, butylmethacrylate (“BMA”), butyl acrylate (“BA”), isobutyl methacrylate(“IBMA”), hexyl methacrylate, cyclohexyl methacrylate, cyclohexylacrylate and mixtures thereof.

[0032] “Mid cut” alkyl (meth)acrylates are typically those where thealkyl group contains from 7 to 15 carbon atoms. Suitable mid cut alkyl(meth)acrylates include, but are not limited to: 2-ethylhexyl acrylate(“EHA”), 2-ethylhexyl methacrylate, octyl methacrylate, decylmethacrylate, isodecyl methacrylate (“IDMA”, based on branched(C₁₀)alkyl isomer mixture), undecyl methacrylate, dodecyl methacrylate(also known as lauryl metharylate), tridecyl methacrylate, tetradecylmethacrylate (also known as myristyl methacrylate), pentadecylmethacrylate and mixtures thereof. Particularly useful mixtures includedodecyl-pentadecyl methacrylate (“DPMA”), a mixture of linear andbranched isomers of dodecyl, tridecyl, tetradecyl and pentadecylmethacrylates; and lauryl-myristyl methacrylate (“LMA”).

[0033] “High cut” alkyl (meth)acrylates are typically those where thealkyl group contains from 16 to 24 carbon atoms. Suitable high cut alkyl(meth)acrylates include, but are not limited to: hexadecyl methacrylate,heptadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate,cosyl methacrylate, eicosyl methacrylate and mixtures thereof.Particularly useful mixtures of high cut alkyl (meth)acrylates include,but are not limited to: cetyl-eicosyl methacrylate (“CEMA”), which is amixture of hexadecyl, octadecyl, cosyl and eicosyl methacrylate; andcetyl-stearyl methacrylate (“SMA”), which is a mixture of hexadecyl andoctadecyl methacrylate.

[0034] The mid-cut and high-cut alkyl (meth)acrylate monomers describedabove are generally prepared by standard esterification procedures usingtechnical grades of long chain aliphatic alcohols, and thesecommercially available alcohols are mixtures of alcohols of varyingchain lengths containing between 10 and 15 or 16 and 20 carbon atoms inthe alkyl group. Examples of these alcohols are the various Zieglercatalyzed ALFOL alcohols from Vista Chemical company, i.e., ALFOL 1618and ALFOL 1620, Ziegler catalyzed various NEODOL alcohols from ShellChemical Company, i.e. NEODOL 25L, and naturally derived alcohols suchas Proctor & Gamble's TA-1618 and CO-1270. Consequently, for thepurposes of this invention, alkyl (meth)acrylate is intended to includenot only the individual alkyl (meth)acrylate product named, but also toinclude mixtures of the alkyl (meth)acrylates with a predominant amountof the particular alkyl (meth)acrylate named.

[0035] The alkyl (meth)acrylate monomers useful in the present inventionmay be a single monomer or a mixture having different numbers of carbonatoms in the alkyl portion. Also, the (meth)acrylamide and alkyl(meth)acrylate monomers useful in the present invention may optionallybe substituted. Suitable optionally substituted (meth)acrylamide andalkyl (meth)acrylate monomers include, but are not limited to: hydroxy(C₂-C₆)alkyl (meth)acrylates, dialkylamino(C₂-C₆)-alkyl (meth)acrylates,dialkylamino(C₂-C₆)alkyl (meth)acrylamides.

[0036] Particularly useful substituted alkyl (meth)acrylate monomers arethose with one or more hydroxyl groups in the alkyl radical, especiallythose where the hydroxyl group is found at the β-position (2-position)in the alkyl radical. Hydroxyalkyl (meth)acrylate monomers in which thesubstituted alkyl group is a (C₂-C₆)alkyl, branched or unbranched, arepreferred. Suitable hydroxyalkyl (meth)acrylate monomers include, butare not limited to: 2-hydroxyethyl methacrylate (“HEMA”), 2-hydroxyethylacrylate (“HEA”), 2-hydroxypropyl methacrylate, 1-methyl-2-hydroxyethylmethacrylate, 2-hydroxy-propyl acrylate, 1-methyl-2-hydroxyethylacrylate, 2-hydroxybutyl methacrylate, 2-hydroxybutyl acrylate andmixtures thereof. The preferred hydroxyalkyl (meth)acrylate monomers areHEMA, 1-methyl-2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylateand mixtures thereof. A mixture of the latter two monomers is commonlyreferred to as “hydroxypropyl methacrylate” or “HPMA.”

[0037] Other substituted (meth)acrylate and (meth)acrylamide monomersuseful in the present invention are those with a dialkylamino group ordialkylaminoalkyl group in the alkyl radical. Examples of suchsubstituted (meth)acrylates and (meth)acrylamides include, but are notlimited to: dimethylaminoethyl methacrylate, dimethylaminoethylacrylate, N,N-dimethylaminoethyl methacrylamide,N,N-dimethyl-aminopropyl methacrylamide, N,N-dimethylaminobutylmethacrylamide, N,N-di-ethylaminoethyl methacrylamide,N,N-diethylaminopropyl methacrylamide, N,N-diethylaminobutylmethacrylamide, N-(1,1-dimethyl-3-oxobutyl) acrylamide,N-(1,3-diphenyl-1-ethyl-3-oxobutyl) acrylamide,N-(1-methyl-1-phenyl-3-oxobutyl) methacrylamide, and 2-hydroxyethylacrylamide, N-methacrylamide of aminoethyl ethylene urea, N-methacryloxyethyl morpholine, N-maleimide of dimethylaminopropylamine and mixturesthereof.

[0038] Other substituted (meth)acrylate monomers useful in the presentinvention are silicon-containing monomers such as γ-propyltri(C₁-C₆)alkoxysilyl (meth)acrylate, γ-propyl tri(C₁-C₆)alkylsilyl(meth)acrylate, γ-propyl di(C₁-C₆)alkoxy(C₁-C₆)alkylsilyl(meth)acrylate, γ-propyl di(C₁-C₆)alkyl(C₁-C₆)alkoxysilyl(meth)acrylate, vinyl tri(C₁-C₆)alkoxysilyl (meth)acrylate, vinyldi(C₁-C₆)alkoxy(C₁-C₆)alkylsilyl (meth)acrylate, vinyl(C₁-C₆)alkoxydi(C₁-C₆)alkylsilyl (meth)acrylate, vinyltri(C₁-C₆)alkylsilyl (meth)acrylate, and mixtures thereof.

[0039] The vinylaromatic monomers useful as unsaturated monomers in thepresent invention include, but are not limited to: styrene (“STY”),α-methylstyrene, vinyltoluene, p-methylstyrene, ethylvinylbenzene,vinylnaphthalene, vinylxylenes, and mixtures thereof. The vinylaromaticmonomers also include their corresponding substituted counterparts, suchas halogenated derivatives, i.e., containing one or more halogen groups,such as fluorine, chlorine or bromine; and nitro, cyano, (C₁-C₁₀)alkoxy,halo(C₁-C₁₀)alkyl, carb(C₁-C₁₀)alkoxy, carboxy, amino,(C₁-C₁₀)alkylamino derivatives and the like.

[0040] The nitrogen-containing compounds and their thio-analogs usefulas unsaturated monomers in the present invention include, but are notlimited to: vinylpyridines such as 2-vinylpyridine or 4-vinylpyridine;lower alkyl (C₁-C₈) substituted N-vinyl pyridines such as2-methyl-5-vinyl-pyridine, 2-ethyl-5-vinylpyridine,3-methyl-5-vinylpyridine, 2,3-dimethyl-5-vinyl-pyridine, and2-methyl-3-ethyl-5-vinylpyridine; methyl-substituted quinolines andisoquinolines; N-vinylcaprolactam; N-vinylbutyrolactam;N-vinylpyrrolidone; vinyl imidazole; N-vinyl carbazole;N-vinyl-succinimide; (meth)acrylonitrile; o-, m-, or p-aminostyrene;maleimide; N-vinyl-oxazolidone; N,N-dimethyl aminoethyl-vinyl-ether;ethyl-2-cyano acrylate; vinyl acetonitrile; N-vinylphthalimide;N-vinyl-pyrrolidones such as N-vinyl-thio-pyrrolidone, 3methyl-1-vinyl-pyrrolidone, 4-methyl-1-vinyl-pyrrolidone,5-methyl-1-vinyl-pyrrolidone, 3-ethyl-1-vinyl-pyrrolidone,3-butyl-1-vinyl-pyrrolidone, 3,3-dimethyl-1-vinyl-pyrrolidone,4,5-dimethyl-1-vinyl-pyrrolidone, 5,5-dimethyl-1-vinyl-pyrrolidone,3,3,5-trimethyl-1-vinyl-pyrrolidone, 4-ethyl-1-vinyl-pyrrolidone,5-methyl-5-ethyl-1-vinyl-pyrrolidone and3,4,5-trimethyl-1-vinyl-pyrrolidone; vinyl pyrroles; vinyl anilines; andvinyl piperidines.

[0041] The substituted ethylene monomers useful as unsaturated monomersis in the present invention include, but are not limited to: allylicmonomers, vinyl acetate, vinyl formamide, vinyl chloride, vinylfluoride, vinyl bromide, vinylidene chloride, vinylidene fluoride andvinylidene bromide.

[0042] The emulsion polymers of the present invention may optionally becross-linked, and preferably are cross-linked. Such cross-linked polymerparticles are particularly useful as porogens in the manufacture ofporous dielectric materials. Any amount of cross-linker is suitable foruse in the present invention. Typically, the polymers of the presentinvention contain at least 1% by weight, based on the total weight ofthe polymer. Up to and including 100% cross-linking agent, based on theweight of the polymer, may be effectively used in the particles of thepresent invention. It is preferred that the amount of cross-linker isfrom about 1% to about 80%, and more preferably from about 1% to about60%.

[0043] Suitable cross-linkers useful in the present invention includedi-, tri-, tetra-, or higher multi-functional ethylenically unsaturatedmonomers. Examples of cross-linkers useful in the present inventioninclude, but are not limited to: trivinylbenzene, divinyltoluene,divinylpyridine, divinylnaphthalene and divinylxylene; and such asethyleneglycol diacrylate, trimethylolpropane triacrylate,diethyleneglycol divinyl ether, trivinylcyclohexane, allyl methacrylate(“ALMA”), ethyleneglycol dimethacrylate (“EGDMA”), diethyleneglycoldimethacrylate (“DEGDMA”), propyleneglycol dimethacrylate,propyleneglycol diacrylate, trimethylolpropane trimethacrylate(“TMPTMA”), divinyl benzene (“DVB”), glycidyl methacrylate,2,2-dimethylpropane 1,3 diacrylate, 1,3-butylene glycol diacrylate,1,3-butylene glycol dimethacrylate, 1,4-butanediol diacrylate,diethylene glycol diacrylate, diethylene glycol dimethacrylate,1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, tripropyleneglycol diacrylate, triethylene glycol dimethacrylate, tetraethyleneglycol diacrylate, polyethylene glycol 200 diacrylate, tetraethyleneglycol dimethacrylate, polyethylene glycol dimethacrylate, ethoxylatedbisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate,polyethylene glycol 600 dimethacrylate, poly(butanediol) diacrylate,pentaerythritol triacrylate, trimethylolpropane triethoxy triacrylate,glyceryl propoxy triacrylate, pentaerythritol tetraacrylate,pentaerythritol tetramethacrylate, dipentaerythritolmonohydroxypentaacrylate, divinyl silane,. trivinyl silane, dimethyldivinyl silane, divinyl methyl silane, methyl trivinyl silane, diphenyldivinyl silane, divinyl phenyl silane, trivinyl phenyl silane, divinylmethyl phenyl silane, tetravinyl silane, dimethyl vinyl disiloxane,poly(methyl vinyl siloxane), poly(vinyl hydro siloxane), poly (phenylvinyl siloxane) and mixtures thereof.

[0044] Particularly suitable monomers for use in the present inventioninclude silyl containing monomers or poly(alkylene oxide) monomers. Suchsilyl containing monomers or poly(alkylene oxide) monomers may be usedto form the uncrosslinked polymer, used as the crosslinker, or both. Anymonomer containing silicon may be useful as the silyl containingmonomers in the present invention. The silicon moiety in such silylcontaining monomers may be reactive or unreactive. Exemplary “reactive”silyl containing monomers include those containing one or more alkoxy oracetoxy groups, such as, but not limited to, trimethoxysilyl containingmonomers, triethoxysilyl containing monomers, methyl dimethoxysilylcontaining monomers, and the like. Exemplary “unreactive” silylcontaining monomers include those containing alkyl groups, aryl groups,alkenyl groups or mixtures thereof, such as but are not limited to,trimethylsilyl containing monomers, triethylsilyl containing monomers,phenyldimethylsilyl containing monomers, and the like. Polymericporogens including silyl containing monomers as polymerized units areintended to include such porogens prepared by the polymerization of amonomer containing a silyl moiety. It is not intended to include alinear polymer that contains a silyl moiety only as end capping units.It is preferred that the silyl containing monomer is not a siloxane. Itis further preferred that the present aqueous emulsion is free ofsiloxane monomer.

[0045] Suitable silyl containing monomers include, but are not limitedto, vinyltrimethylsilane, vinyltriethylsilane, vinyltrimethoxysilane,vinyltriethoxysilane, γ-trimethoxysilylpropyl (meth)acrylate,divinylsilane, trivinylsilane, dimethyldivinylsilane,divinylmethylsilane, methyltrivinylsilane, diphenyldivinylsilane,divinylphenylsilane, trivinylphenylsilane, divinylmethylphenylsilane,tetravinylsilane, allyloxy-tert-butyldimethylsilane,allyloxytrimethylsilane, allyltriethoxysilane,allyltri-iso-propylsilane, allyltrimethoxysilane, allyltrimethylsilane,allyltriphenylsilane, diethoxy methylvinylsilane, diethylmethylvinylsilane, dimethyl ethoxyvinylsilane, dimethylphenylvinylsilane, ethoxy diphenylvinylsilane, methylbis(trimethylsilyloxy)vinylsilane, triacetoxyvinylsilane,triethoxyvinylsilane, triethylvinylsilane, triphenylvinylsilane,tris(trimethylsilyloxy)vinylsilane, vinyloxytrimethylsilane and mixturesthereof.

[0046] The amount of silyl containing monomer useful to form theparticles of the present invention is typically from about 1 to about99% wt, based on the total weight of the monomers used. It is preferredthat the silyl containing monomers are present in an amount of from 1 toabout 80% wt, and more preferably from about 5 to about 75% wt.

[0047] Suitable poly(alkylene oxide) monomers include, but are notlimited to, poly(propylene oxide) monomers, poly(ethylene oxide)monomers, poly(ethylene oxide/propylene oxide) monomers, poly(propyleneglycol) (meth)acrylates, poly(propylene glycol) alkyl ether(meth)acrylates, poly(propylene glycol) phenyl ether (meth)acrylates,poly(propylene glycol) 4-nonylphenol ether (meth)acrylates,poly(ethylene glycol) (meth)acrylates, poly(ethylene glycol) alkyl ether(meth)acrylates, poly(ethylene glycol) phenyl ether (meth)acrylates,poly(propylene/ethylene glycol) alkyl ether (meth)acrylates and mixturesthereof. Preferred poly(alkylene oxide) monomers includetrimethoylolpropane ethoxylate tri(meth)acrylate, trimethoylolpropanepropoxylate tri(meth)acrylate, poly(propylene glycol) methyl etheracrylate, and the like. Particularly suitable poly(propylene glycol)methyl ether acrylate monomers are those having a molecular weight inthe range of from about 200 to about 2000. The poly(ethyleneoxide/propylene oxide) monomers useful in the present invention may belinear, block or graft copolymers. Such monomers typically have a degreeof polymerization of from about 1 to about 50, and preferably from about2 to about 50.

[0048] Typically, the amount of poly(alkylene oxide) monomers useful inthe particles of the present invention is from about 1 to about 99% wt,based on the total weight of the monomers used. The amount ofpoly(alkylene oxide) monomers is preferably from about 2 to about 90%wt, and more preferably from about 5 to about 80% wt.

[0049] The emulsion polymers useful in the present invention aregenerally prepared by first charging water and some portion of themonomer emulsion to a reaction vessel equipped with a stirrer, athermometer and a reflux condenser. Typically, the monomer emulsion iscomposed of monomer, surfactant, initiator and chain transfer agent, asappropriate. The initial charge of monomer emulsion is heated withstirring under a nitrogen blanket to a temperature of from about 55° C.to about 125° C. After the seed charge has reached a temperaturesufficient to initiate polymerization, the monomer emulsion or balanceof the monomer emulsion is charged to the reaction vessel over a periodof 15 minutes to 4 hours while maintaining the reaction at the desiredreaction temperature. After completing the monomer emulsion addition, aseries of additional aliquots of initiator in water are charged to thereaction. Typically the initiator is charged to the reaction andfollowed by a hold period to allow for reaction to occur before addingthe next initiator amount. Typically three initiator additions are used.After the final initiator amount is added, the batch is held for 30minutes to 4 hours to fully decompose all initiator and drive thereaction to completeness.

[0050] In the alternative, the emulsion polymerization may be carriedout in a batch process. In such a batch process, the emulsion polymersare prepared by charging water, monomer, surfactant, initiator and chaintransfer agent, as appropriate, to a reaction vessel with stirring undera nitrogen blanket. The monomer emulsion is heated to a temperature offrom about 55° C. to about 125° C. to carry out the polymerization.After 30 minutes to 4 hours at this temperature, a series of additionalaliquots of initiator are charged to the reaction vessel. Typically theinitiator is charged to the reaction vessel followed by a hold period toallow for reaction to occur before adding the next amount of initiator.Typically three initiator additions are used. After the final initiatoramount is added, the batch is held for 30 minutes to 4 hours to fullydecompose all initiator and drive the reaction to completeness.

[0051] It is preferred that the polymers of the present invention areprepared using anionic polymerization or free radical polymerizationtechniques. Initiators useful in the free radical polymerization ofporogens of the present invention include, but are not limited to, oneor more of: peroxyesters, dialkylperoxides, alkylhydroperoxides,persulfates, azoinitiators, redox initiators and the like. Particularlyuseful free radical initiators include, but are not limited to: benzoylperoxide, t-butyl peroctoate, t-amyl peroxypivalate, cumenehydroperoxide, and azo compounds such as azoisobutylnitrile and2,2′-azobis (2-methylbutanenitrile). When such free radical initiatorsare used, part of the initiator is incorporated into the polymer as endgroups. The amount of the free radical initiator used is typically from0.05 to 10% by weight, based on the weight of total monomer.

[0052] Chain transfer reagents may optionally be used to prepare thepolymers useful in the present invention. Suitable chain transfer agentsinclude, but are not limited to: alkyl mercaptans such as dodecylmercaptan, and aromatic hydrocarbons with activated hydrogens such astoluene. When the porous dielectric material of the present invention isused in a semiconductor, it is preferred that the optional chaintransfer agent is not a sulfur-containing chain transfer agent.

[0053] The present polymer particles have the advantage overconventionally produced emulsion polymer particles in that they have amuch lower level of ions in solution. Preferably, the present polymerparticles are substantially free of ionic impurities, including ionicsurfactants. Such polymer particles being substantially free of ionicimpurities are particularly suitable for use in electronic applications.The present invention thus reduces or eliminates the need to carry outsubsequent purification steps of the polymer particles, such as dialysisor ultra-filtration, to remove the unwanted ionic impurities. Inaddition, the use of nonionic surfactants allows for easier transfer ofthe particles into organic solvents. This is often required to use theparticles as the materials, such as B-staged dielectric materials, intowhich they will be subsequently dispersed are soluble primarily inorganic solvents such as alcohols, amides, esters, ethers, ketones,aromatic or aliphatic hydrocarbons and the like.

[0054] Thus, the present invention provides an emulsion of polymerparticles including one or more surfactants, the one or more surfactantsconsisting of nonionic surfactants, wherein at least one of the nonionicsurfactants is an amine-N-oxide surfactant, and wherein the polymerparticles have a mean particle size of less than or equal to 100 nm. Thepresent invention further provides an emulsion of polymer particlesincluding one or more surfactants, wherein the polymer particles have amean particle size of less than or equal to 100 nm, and wherein theemulsion is substantially free of ionic surfactants.

[0055] The present polymer particles can be redispersed in an organicsolvent by a number of techniques known to those skilled in the artincluding but not limited to freeze-drying, spray drying, solventexchange, dialysis, and azeotropic distillation.

[0056] It was surprisingly found that nonionic surfactants alone,wherein at least one nonionic surfactant is an amine-oxide surfactant,are capable of producing polymer particles having small particle sizes.

[0057] The polymer particles of the present invention are suitable for avariety of uses. Suitable uses are any where conventional emulsionpolymer particles are used, such as in coatings such as paints,varnishes, and the like; adhesives; construction products such asmastics, caulks, sealants, and the like; polishes; waxes; electronicapplications such as in photoresists, plating resists, soldermasks,antireflective coatings, and as porogens for use in forming porousmaterials; and optoelectronic applications such as coatings, films, andfor attenuating the refractive index of materials such as waveguides,optical switches, and the like.

[0058] The emulsion polymer particles of the present invention areuseful as porogens in reducing the dielectric constant of dielectricmaterials, particularly low dielectric constant (“k”) materials. A low kdielectric material is any material having a dielectric constant lessthan 4. Suitable dielectric materials useful in the present inventioninclude, but are not limited to: inorganic matrix materials such ascarbides, oxides, nitrides and oxyfluorides of silicon, boron, oraluminum; silicones; siloxanes, such as silsesquioxanes; silicates;silazanes; and organic matrix materials such as benzocyclobutenes,poly(aryl esters), poly(ether ketones), polycarbonates, polyimides,fluorinated polyimides, polynorbomenes, poly(arylene ethers),polyaromatic hydrocarbons, such as polynaphthalene, polyquinoxalines,poly(perfluorinated hydrocarbons) such as poly(tetrafluoroethylene), andpolybenzoxazoles. Particularly suitable dielectric materials areavailable under the tradenames TEFLON, AVATREL, BCB, AEROGEL, XEROGEL,PARYLENE F, and PARYLENE N. Suitable silsesquioxane compositionsinclude, but are not limited to hydrogen silsesquioxane, alkylsilsesquioxane such as methyl silsesquioxane, aryl silsesquioxane suchas phenyl silsesquioxane, and mixtures thereof, such as alkyl/hydrogen,aryl/hydrogen or alkyl/aryl silsesquioxane. It is preferred that thedielectric material is a silsesquioxane and more preferably hydrogensilsesquioxane, methyl silsesquioxane, phenyl silsesquioxane, a mixtureof dielectric materials containing hydrogen silsesquioxane as apredominant component, or mixtures thereof. Such dielectric materialsare commercially available or may be prepared by known methods. Forexample the preparation of hydrogen silsesquioxanes is disclosed in U.S.Pat. No. 3,615,272. Typically, the silsesquioxanes useful in the presentinvention are used as oligomeric materials, generally having from 8 to20 repeating units.

[0059] Preferred dielectric materials are B-staged organo polysilicamaterials. By B-staged organo polysilica (or organo siloxane) is meant acompound including silicon, carbon, oxygen and hydrogen atoms and havingthe formula:

((RR¹SiO)_(a)(R²SiO_(1.5))_(b)(R³SiO_(1.5))_(c)(SiO₂)_(d))_(n)

[0060] wherein R, R¹, R² and R³ are independently selected fromhydrogen, (C₁-C₆)alkyl, aryl, and substituted aryl; a, c and d areindependently a number from 0 to 1; b is a number from 0.2 to 1; n isinteger from about 3 to about 10,000; provided that a+b+c+d=1; andprovided that at least one of R, R¹ and R² is not hydrogen. “Substitutedaryl” refers to an aryl group having one or more of its hydrogensreplaced by another substituent group, such as cyano, hydroxy, mercapto,halo, (C₁-C₆)alkyl, (C₁-C₆)alkoxy, and the like. In the above formula,a, b, c and d represent the mole ratios of each component. Such moleratios can be varied between 0 and about 1. It is preferred that a isfrom 0 to about 0.8. It is also preferred that c is from 0 to about 0.8.It is further preferred that d is from 0 to about 0.8. In the aboveformula, n refers to the number of repeat units in the B-stagedmaterial. Preferably, n is an integer from about 3 to about 1000. Itwill be appreciated that prior to any curing step, the B-staged organopolysilica dielectric matrix materials may include one or more ofhydroxyl or alkoxy end capping or side chain functional groups. Such endcapping or side chain functional groups are known to those skilled inthe art.

[0061] When used as porogens, the present polymer particles may bedirectly added to a B-staged dielectric matrix material as is or may befirst purified to remove impurities that might affect the electrical orphysical properties of electronic devices. Purification of the porogenparticles may be accomplished either by precipitation of the porogenparticles or adsorption of the impurities. It will be appreciated bythose skilled in the art that by preparing the present polymer particlesin nonionic surfactants, the amount of ionic impurities to be removed isgreatly reduced. The present emulsion particles when used as porogenstypically have a weight average molecular weight in the range of 1000 to10,000,000, preferably 100,000 to 5,000,000, and more preferably 100,000to 1,000,000.

[0062] In preparing the dielectric matrix materials of the presentinvention, the porogens are first dispersed within, or dissolved in, aB-staged dielectric material. Any amount of porogen may be combined withthe B-staged dielectric materials according to the present invention.The amount of porogen used will depend on the particular porogenemployed, the particular B-staged dielectric material employed, and theextent of dielectric constant reduction desired in the resulting porousdielectric material. Typically, the amount of porogen used is in therange of from 1 to 90 wt %, based on the weight of the B-stageddielectric material, preferably from 10 to 80 wt %, more preferably from15 to 60 wt %, and even more preferably from 20 to 30 wt %. Typically,the B-staged matrix material is first dissolved in a suitable highboiling solvent, such as methyl isobutyl ketone, diisobutyl ketone,2-heptanone, γ-butyrolactone, γ-caprolactone, ethyl lactatepropyleneglycol monomethyl ether acetate, propyleneglycol monomethylether, diphenyl ether, anisole, n-amyl acetate, n-butyl acetate,cyclohexanone, N-methyl-2-pyrrolidone, N,N′-dimethylpropyleneurea,mesitylene, xylenes, or mixtures thereof to form a solution. The porogenparticles are then dispersed or dissolved within the solution. Theresulting dispersion is then deposited on a substrate by methods knownin the art, such as spin coating, spray coating or doctor blading, toform a film or layer. Thus, the present invention still further providesa composition including a B-staged dielectric material and an emulsionpolymeric porogen particle wherein the polymer particles have a meanparticle size of less than or equal to 100 nm, and wherein the polymerparticles are substantially free of ionic surfactants. Preferably, theemulsion polymeric porogen particle includes one or more amine-N-oxidesurfactants.

[0063] After being deposited on a substrate, the B-staged dielectricmaterial is then substantially cured to form a rigid, cross-linkeddielectric matrix material without substantially removing the porogenparticle. Such curing may be by any means known in the art including,but not limited to, heating to induce condensation or e-beam irradiationto facilitate free radical coupling of the oligomer or monomer units.

[0064] Once the B-staged dielectric material is cured, the film issubjected to conditions which remove the porogen without substantiallydegrading the dielectric matrix material, that is, less than 5% byweight of the dielectric matrix material is lost. Typically, suchconditions include exposing the film to heat and/or radiation and arewithin the ability of one skilled in the art. Upon removal, the porogenpolymer depolymerizes or otherwise breaks down into volatile componentsor fragments which are then removed from, or migrate out of, thedielectric matrix material yielding pores or voids, which fill up withthe carrier gas used in the process. Thus, a porous dielectric materialhaving voids is obtained, where the size of the voids is substantiallythe same as the particle size of the porogen. The resulting dielectricmaterial having voids thus has a lower dielectric constant than suchmaterial without such voids.

[0065] The present emulsion particles may also be post-functionalized.Such post-functionalization may be advantageous, such as in furthercompatiblizing the porogen with the dielectric material and may be byany techniques known in the art. It is preferred that when the polymerparticles of the present invention are used as porogens, that they aresubstantially compatible with the dielectric material.

[0066] In general, the emulsion polymers of the present invention usefulas porogens must be dispersible, miscible or otherwise substantiallycompatible with the host dielectric matrix material in solution and inthe thin film. Preferably, the porogen must be present within thissolution as substantially discrete, substantially non-aggregated orsubstantially non-agglomerated particles in order to achieve the desiredbenefit of this invention, namely substantially uniformly dispersedpores with a size comparable to that of the porogen's size. This isaccomplished by modifying the porogen composition such that it is“compatible” with the host dielectric matrix material. Suchcompatibilization is described in copending U.S. Pat. App. Ser. No.09/460,326 (Allen et al.).

[0067] In a further embodiment, the present invention provides a methodof manufacturing an electronic device including the steps of: a)depositing on a substrate a layer of a composition including B-stageddielectric material having a plurality of emulsion polymeric porogenparticles dispersed therein, wherein the porogen particles have a meanparticle size of less than or equal to 1100 nm, and wherein the porogenparticles are substantially free of ionic surfactants; b) curing theB-staged dielectric material to form a dielectric matrix materialwithout substantially removing the porogen particles; c) subjecting thedielectric matrix material to conditions which at least partially removethe porogen particles to form a porous dielectric material layer withoutsubstantially degrading the dielectric material; d) patterning thedielectric layer; e) depositing a metallic film onto the patterneddielectric layer; and f) planarizing the film to form an electronicdevice. Preferably, the porogen is substantially compatible with theB-staged dielectric material.

[0068] The porous dielectric material may be lithographically patternedby a variety of means known in the art, such as by using photoresists.Such patterning typically forms vias and/or trenches in subsequentprocessing steps. The trenches generally extend to the substrate andconnect to at least one metallic via. Typically, lithographic patterninginvolves (i) coating the dielectric material layer with a positive ornegative photoresist, such as those marketed by Shipley Company(Marlborough, Mass.); (ii) imagewise exposing, through a mask, thephotoresist to radiation, such as light of appropriate wavelength ore-beam; (iii) developing the image in the resist, e.g., with a suitabledeveloper; and (iv) transferring the image through the dielectric layerto the substrate with a suitable transfer technique such as reactive ionbeam etching. Optionally, an antireflective composition may be disposedon the dielectric material prior to the photoresist coating. Suchlithographic patterning techniques are well known to those skilled inthe art.

[0069] A metallic film is then deposited onto the patterned dielectriclayer to fill the trenches. Preferred metallic materials include, butare not limited to: copper, tungsten, gold, silver, aluminum or alloysthereof. The metal is typically deposited onto the patterned dielectriclayer by techniques well known to those skilled in the art. Suchtechniques include, but are not limited to: chemical vapor deposition(“CVD”), plasma-enhanced CVD, combustion CVD (“CCVD”), electro andelectroless deposition, sputtering, or the like. Optionally, a metallicliner, such as a layer of nickel, tantalum, titanium, tungsten, orchromium, including nitrides or silicides thereof, or other layers suchas barrier or adhesion layers, e.g. silicon nitride or titanium nitride,is deposited on the patterned and etched dielectric material.

[0070] Excess metallic material is removed, e.g. by planarizing themetallic film, so that the resulting metallic material is generallylevel with the patterned dielectric layer. Planarization is typicallyaccomplished with chemical/mechanical polishing or selective wet or dryetching. Such planarization methods are well known to those skilled inthe art.

[0071] It will be appreciated by those skilled in the art that multiplelayers of dielectric material, including multiple layers of porousdielectric material, and metal layers may subsequently be applied byrepeating the above steps. It will be further appreciated by thoseskilled in the art that the compositions of the present invention areuseful in any and all methods of integrated circuit manufacture.

[0072] The following examples are presented to illustrate furthervarious aspects of the present invention, but are not intended to limitthe scope of the invention in any aspect.

EXAMPLE 1 (COMPARATIVE)

[0073] A plurality of emulsion polymer particles was prepared by agradual-add polymerization process. A monomer emulsion was made from amixture of 100 g water, 1.60 g of 28% w/w solids SLS, 50.7 g styrene(“STY”) and 16.9 g divinyl benzene (“DVB”). A reaction kettle containing445 g water, 22.2 g of 28% w/w solids SLS and 0.37 g ammonium persulfatewas heated to 85° C. under a nitrogen atmosphere. The monomer emulsionwas fed to the kettle over 90 minutes. The reaction was held at 85° C.for 30 minutes after the end of the feed, and then cooled to 65° C.After cooling, 1.33 g of 10% iron sulfate (FeSO₄) was added. After 1minute, 0.2 g of 70% tert-butyl hydroperoxide (“t-BHP”) was added andafter 2 minutes 0.10 g of 100% isoascorbic acid (“IAA”) and the reactionheld for 15 minutes. A second chaser system was added in the samesequence and over the same time period. The reaction was then cooled toambient temperature and filtered through a 400 mesh sieve. The meanparticle size of this sample (Comparative C-1) was determined to be 22nm.

EXAMPLES 2-4 (COMPARATIVE)

[0074] The procedures of Example 1 were repeated, except that the amountof STY, DVB, and surfactant level were changed. Also, Comparatives C-3and C-4 contained a second monomer. The particular components and theiramounts are reported in the Table. Also reported are the mean particlesizes for these samples. TABLE STY DVB Additional Surfactant MeanParticle Sample (wt %) (wt %) Monomer (wt %) Size (nm) C-2 82 18 — SLS(5 wt %) 34 C-3 72 18 A-MSTY ALS (5 wt %) 39 (10 wt %) C-4 12 18 MMA ALS(10 wt %) 22

EXAMPLE 5

[0075] A plurality of emulsion polymer particles was prepared by agradual-add polymerization process. A monomer emulsion was made from amixture of 100 g water, 1.60 g of 28% w/w solidslauryldimethylamine-N-oxide, 55.1 g styrene and 12.5 g divinyl benzene.A reaction kettle containing 445 g water, 10.3 g of 28% w/w solidslauryldimethylamine-N-oxide (ca. 5 wt %) and 0.37 g ammonium persulfatewas heated to 85° C. under a nitrogen atmosphere. The monomer emulsionwas fed to the kettle over 90 minutes. The reaction was held at 85° C.for 30 minutes after the end of the feed, and then cooled to 65° C.After cooling, 1.33 g of 10% iron sulfate (FeSO₄) was added. After 1minute, 0.2 g of 70% t-BHP was added and after 2 minutes 0.10 g of 100%isoascorbic acid (“IAA”) and the reaction held for 15 minutes. A secondchaser system was added in the same sequence and over the same timeperiod. The reaction was then cooled to ambient temperature and filteredthrough a 400 mesh sieve. The mean particle size of the emulsionparticles was determined to be 39 nm. Thus, the use of a nonionicamine-oxide surfactant produced emulsion particles having an extremelysmall mean particle size.

EXAMPLE 6

[0076] A plurality of emulsion polymer particles was prepared by agradual-add polymerization process. A monomer emulsion was made from amixture of 100 g water, 1.60 g of 28% w/w solidslauryldimethylamine-N-oxide, 55.1 g styrene and 12.5 g divinyl benzene.A reaction kettle containing 445 g water, 22.2 g of 28% w/w solidslauryldimethylamine-N-oxide (ca. 10 wt %) and 0.37 g ammonium persulfatewas heated to 85° C. under a nitrogen atmosphere. The monomer emulsionwas fed to the kettle over 90 minutes. The reaction was held at 85° C.for 30 minutes after the end of the feed, and then cooled to 65° C.After cooling, 1.33 g of 10% iron sulfate (FeSO₄) was added. After 1minute, 0.2 g of 70% t-BHP was added and after 2 minutes 0.10 g of 100%isoascorbic acid (“IAA”) and the reaction held for 15 minutes. A secondchaser system was added in the same sequence and over the same timeperiod. The reaction was then cooled to ambient temperature and filteredthrough a 400 mesh sieve. The mean particle size of the emulsionparticles was determined to be 22 nm. Thus, the use of a nonionicamine-oxide surfactant produced emulsion particles having an extremelysmall mean particle size.

What is claimed is:
 1. A process for preparing polymer particlescomprising the step of: polymerizing one or more monomers in an aqueousemulsion comprising one or more surfactants, the one or more surfactantsconsisting of nonionic surfactants, wherein at least one of the nonionicsurfactants is an amine-N-oxide surfactant, and wherein the polymerparticles have a mean particle size of less than or equal to 100 nm. 2.The process of claim 1 wherein the amine-N-oxide surfactant is selectedfrom N-alkyl amine oxides, N-acyl amine oxides or N-alkoxyalkyl amineoxides.
 3. The process of claim 2 wherein the amine-N-oxide is selectedfrom N-cocodimethylamine oxide, N-lauryl dimethylamine oxide, N-myristyldimethylamine oxide, N-stearyl dimethylamine oxide; N-cocamidopropyldimethylamine oxide, N-tallowamidopropyl dimethylamine oxide, orbis(2-hydroxyethyl) C₁₂-₁₅ alkoxypropylamine oxide.
 4. The process ofclaim 3 wherein the bis(2-hydroxyethyl) C₁₂-₁₅ alkoxypropylamine oxideis selected from lauric acid diethanolamide, coconut aciddiethanolamide, myristic acid diethanolamide, or oleic aciddiethanolamide.
 5. The process of claim 1 further comprising one or morenonionic surfactants selected from ethoxylated fatty alcohols, fattyacid alkanolamides, sorbitan derivatives or ethylene oxide/propyleneoxide copolymers.
 6. The process of claim 1 wherein the mean particlesize of less than or equal to 50 nm.
 7. The process of claim 1 whereinthe anime-N-oxide surfactant is present in an amount from 0.1 to 15% byweight, based on the total weight of the composition.
 8. The process ofclaim 1 wherein at least one monomer is selected from silyl containingmonomers or poly(alkylene oxide) monomers.
 9. The process of claim 1further comprising one or more cross-linking agents.
 10. The process ofclaim 1 wherein the emulsion is free of siloxane monomers.
 11. Anemulsion of polymer particles comprising one or more surfactants, theone or more surfactants consisting of nonionic surfactants, wherein atleast one of the nonionic surfactants is an amine-N-oxide surfactant,and wherein the polymer particles have a mean particle size of less thanor equal to 100 nm.
 12. The emulsion of claim 11 wherein theamine-N-oxide surfactant is selected from N-alkyl amine oxides, N-acylamine oxides or N-alkoxyalkyl amine oxides.
 13. The emulsion of claim 12wherein the amine-N-oxide is selected from N-cocodimethylamine oxide,N-lauryl dimethylamine oxide, N-myristyl dimethylamine oxide, N-stearyldimethylamine oxide; N-cocamidopropyl dimethylamine oxide,N-tallowamidopropyl dimethylamine oxide, or bis(2-hydroxyethyl) C₁₂-15alkoxypropylamine oxide.
 14. The emulsion of claim 13 wherein thebis(2-hydroxyethyl) C₁₂-₁₅ alkoxypropylamine oxide is selected fromlauric acid diethanolamide, coconut acid diethanolamide, myristic aciddiethanolamide, or oleic acid diethanolamide.
 15. The emulsion of claim11 wherein the mean particle size of less than or equal to 50 nm.
 16. Anemulsion of polymer particles comprising one or more nonionicsurfactants, wherein the polymer particles have a mean particle size ofless than or equal to 100 nm, and wherein the emulsion is substantiallyfree of ionic surfactants.
 17. The emulsion of claim 16 wherein at leastone of the nonionic surfactants is an amine-N-oxide surfactant.
 18. Acomposition comprising a B-staged dielectric material and an emulsionpolymeric porogen particle wherein the polymer particles have a meanparticle size of less than or equal to 100 nm, and wherein the polymerparticles are substantially free of ionic surfactants.
 19. Thecomposition of claim 18 wherein the B-staged dielectric material isselected from silicon carbides, boron carbides, aluminum carbides,silicon oxides, boron oxides, aluminum oxides, silicon nitrides, boronnitrides, aluminum nitrides, silicon oxyfluorides, boron oxyfluorides,aluminum oxyfluorides, silicones, siloxanes, benzocyclobutenes,poly(aryl esters), poly(ether ketones), polycarbonates, polyimides,fluorinated polyimides, polynorbomenes, poly(arylene ethers),polyaromatic hydrocarbons, polyquinoxalines, poly(perfluorinatedhydrocarbons), or polybenzoxazoles.
 20. The composition of claim 18wherein the emulsion polymeric porogen particle comprises one or moreamine-N-oxide surfactants.
 21. A method of manufacturing an electronicdevice comprising the steps of: a) depositing on a substrate a layer ofa composition comprising B-staged dielectric material having a pluralityof emulsion polymeric porogen particles dispersed therein, wherein theporogen particles have a mean particle size of less than or equal to 100nm, and wherein the porogen particles are substantially free of ionicsurfactants; b) curing the B-staged dielectric material to form adielectric matrix material without substantially removing the porogenparticles; c) subjecting the dielectric matrix material to conditionswhich at least partially remove the porogen particles to form a porousdielectric material layer without substantially degrading the dielectricmaterial; d) patterning the dielectric layer; e) depositing a metallicfilm onto the patterned dielectric layer; and f) planarizing the film toform an electronic device.
 22. The method of claim 21 wherein theB-staged dielectric material is an organo polysilica compound having theformula: ((RR¹SiO)_(a)(R²SiO_(1.5))_(b)(R³SiO_(1.5))_(c)(SiO₂)_(d))_(n)wherein R, R¹, R² and R³ are independently selected from hydrogen,(C₁-C₆)alkyl, aryl, and substituted aryl; a, c and d are independently anumber from 0 to 1; b is a number from 0.2 to 1; n is integer from about3 to about 10,000; provided that a+b+c+d=1; and provided that at leastone of R, R¹ and R² is not hydrogen.